Child-welfare workers ignored repeated complaints about an upstate couple now accused of grossly underfeeding a 5-year-old retarded boy in their filthy house of horrors, a former neighbor charged yesterday.

“I called CPS [Child Protective Services] three or four times . . . They went and they didn’t do anything,” said Christina Stevens, who lived next to the Cortland couple and three children last year.

Stevens said that as long ago as April 2005, she pointed out her neighbor Judy Gratton’s public drinking to a visiting social-services worker.

That worker said, “I’ll see what I can do,” Stevens recalled.

But nothing apparently happened to Gratton, 48, and her boyfriend, Joseph Kahn, 45, until last Tuesday, when police conducting a drug raid on their cockroach-infested apartment discovered a heartwrenching scene.

Gratton’s 5-year-old son, Harley, who has Down syndrome, was found wearing soiled diapers, infested with lice and weighing just 15 pounds. Cops found Gratton’s other children, Jodie, 11, and Buddy, 12, also malnourished.

Harley now is in a Syracuse hospital, while the other two children have been placed with the local Social Services Department. Gratton and Kahn have been charged with various counts of child endangerment, in addition to drug charges.

After the raid, about 60 bags of dirty diapers were hauled out of the apartment, which yesterday still emitted a rank odor.

Gratton “would get a [government] check for Harley every month, and instead of buying food, she would buy booze,” said Stevens, who remembered delousing Gratton’s other children after seeing lice jumping off their bodies.

Stevens recalled when Gratton once asked her to buy a can of baby formula for Harley. “This will last me for a week,” Gratton said, according to Stevens.

“I had seen the baby wearing three diapers. She said it was because she never wanted to change the diapers,” Stevens said. Stevens’ 13-year-old daughter, Kayla, said that during 100-degree days, Harley would be kept in a stifling bedroom. On the few occasions he was allowed out of that room, he would sit on a filthy floor with his mother nearby.